usr.bin/tail/forward.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Edward Sze-Tyan Wang.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#)forward.c        8.1 (Berkeley) 6/6/93
  37  * $FreeBSD: src/usr.bin/tail/forward.c,v 1.11.6.7 2003/01/07 05:26:22 tjr Exp $
  38  * $DragonFly: src/usr.bin/tail/forward.c,v 1.6 2005/03/01 21:37:33 cpressey Exp $
  39  */
  40
  41 #include <sys/types.h>
  42 #include <sys/stat.h>
  43 #include <sys/time.h>
  44 #include <sys/mman.h>
  45 #include <sys/event.h>
  46
  47 #include <limits.h>
  48 #include <fcntl.h>
  49 #include <errno.h>
  50 #include <unistd.h>
  51 #include <stdio.h>
  52 #include <stdlib.h>
  53 #include <string.h>
  54 #include <err.h>
  55 #include "extern.h"
  56
  57 static void rlines(FILE *, off_t, struct stat *);
  58
  59 /* defines for inner loop actions */
  60 #define USE_SLEEP       0
  61 #define USE_KQUEUE      1
  62 #define ADD_EVENTS      2
  63
  64 struct kevent *ev;
  65 int action = USE_SLEEP;
  66 int kq;
  67
  68 /*
  69  * forward -- display the file, from an offset, forward.
  70  *
  71  * There are eight separate cases for this -- regular and non-regular
  72  * files, by bytes or lines and from the beginning or end of the file.
  73  *
  74  * FBYTES       byte offset from the beginning of the file
  75  *      REG     seek
  76  *      NOREG   read, counting bytes
  77  *
  78  * FLINES       line offset from the beginning of the file
  79  *      REG     read, counting lines
  80  *      NOREG   read, counting lines
  81  *
  82  * RBYTES       byte offset from the end of the file
  83  *      REG     seek
  84  *      NOREG   cyclically read characters into a wrap-around buffer
  85  *
  86  * RLINES
  87  *      REG     mmap the file and step back until reach the correct offset.
  88  *      NOREG   cyclically read lines into a wrap-around array of buffers
  89  */
  90 void
  91 forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
  92 {
  93         int ch;
  94
  95         switch(style) {
  96         case FBYTES:
  97                 if (off == 0)
  98                         break;
  99                 if (S_ISREG(sbp->st_mode)) {
 100                         if (sbp->st_size < off)
 101                                 off = sbp->st_size;
 102                         if (fseeko(fp, off, SEEK_SET) == -1) {
 103                                 ierr();
 104                                 return;
 105                         }
 106                 } else while (off--)
 107                         if ((ch = getc(fp)) == EOF) {
 108                                 if (ferror(fp)) {
 109                                         ierr();
 110                                         return;
 111                                 }
 112                                 break;
 113                         }
 114                 break;
 115         case FLINES:
 116                 if (off == 0)
 117                         break;
 118                 for (;;) {
 119                         if ((ch = getc(fp)) == EOF) {
 120                                 if (ferror(fp)) {
 121                                         ierr();
 122                                         return;
 123                                 }
 124                                 break;
 125                         }
 126                         if (ch == '\n' && !--off)
 127                                 break;
 128                 }
 129                 break;
 130         case RBYTES:
 131                 if (S_ISREG(sbp->st_mode)) {
 132                         if (sbp->st_size >= off &&
 133                             fseeko(fp, -off, SEEK_END) == -1) {
 134                                 ierr();
 135                                 return;
 136                         }
 137                 } else if (off == 0) {
 138                         while (getc(fp) != EOF);
 139                         if (ferror(fp)) {
 140                                 ierr();
 141                                 return;
 142                         }
 143                 } else
 144                         if (display_bytes(fp, off))
 145                                 return;
 146                 break;
 147         case RLINES:
 148                 if (S_ISREG(sbp->st_mode))
 149                         if (!off) {
 150                                 if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
 151                                         ierr();
 152                                         return;
 153                                 }
 154                         } else
 155                                 rlines(fp, off, sbp);
 156                 else if (off == 0) {
 157                         while (getc(fp) != EOF);
 158                         if (ferror(fp)) {
 159                                 ierr();
 160                                 return;
 161                         }
 162                 } else
 163                         if (display_lines(fp, off))
 164                                 return;
 165                 break;
 166         case REVERSE:
 167                 errx(1, "internal error: forward style cannot be REVERSE");
 168                 /* NOTREACHED */
 169         }
 170
 171         while ((ch = getc(fp)) != EOF) {
 172                 if (putchar(ch) == EOF)
 173                         oerr();
 174         }
 175         if (ferror(fp)) {
 176                 ierr();
 177                 return;
 178         }
 179         fflush(stdout);
 180 }
 181
 182 /*
 183  * rlines -- display the last offset lines of the file.
 184  */
 185 static void
 186 rlines(FILE *fp, off_t off, struct stat *sbp)
 187 {
 188         struct mapinfo map;
 189         off_t curoff, size;
 190         int i;
 191
 192         if (!(size = sbp->st_size))
 193                 return;
 194         map.start = NULL;
 195         map.fd = fileno(fp);
 196         map.mapoff = map.maxoff = size;
 197
 198         /*
 199          * Last char is special, ignore whether newline or not. Note that
 200          * size == 0 is dealt with above, and size == 1 sets curoff to -1.
 201          */
 202         curoff = size - 2;
 203         while (curoff >= 0) {
 204                 if (curoff < map.mapoff && maparound(&map, curoff) != 0) {
 205                         ierr();
 206                         return;
 207                 }
 208                 for (i = curoff - map.mapoff; i >= 0; i--)
 209                         if (map.start[i] == '\n' && --off == 0)
 210                                 break;
 211                 /* `i' is either the map offset of a '\n', or -1. */
 212                 curoff = map.mapoff + i;
 213                 if (i >= 0)
 214                         break;
 215         }
 216         curoff++;
 217         if (mapprint(&map, curoff, size - curoff) != 0) {
 218                 ierr();
 219                 exit(1);
 220         }
 221
 222         /* Set the file pointer to reflect the length displayed. */
 223         if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
 224                 ierr();
 225                 return;
 226         }
 227         if (map.start != NULL && munmap(map.start, map.maplen)) {
 228                 ierr();
 229                 return;
 230         }
 231 }
 232
 233 /*
 234  * follow -- display the file, from an offset, forward.
 235  */
 236
 237 static void
 238 show(file_info_t *file, int at_index)
 239 {
 240         int ch, first;
 241
 242         first = 1;
 243         while ((ch = getc(file->fp)) != EOF) {
 244                 if (first && no_files > 1) {
 245                         showfilename(at_index, file->file_name);
 246                         first = 0;
 247                 }
 248                 if (putchar(ch) == EOF)
 249                         oerr();
 250         }
 251         fflush(stdout);
 252         if (ferror(file->fp)) {
 253                 file->fp = NULL;
 254                 ierr();
 255         } else {
 256                 clearerr(file->fp);
 257         }
 258 }
 259
 260 void
 261 showfilename(int at_index, const char *filename)
 262 {
 263         static int last_index = -1;
 264         static int continuing = 0;
 265
 266         if (last_index == at_index)
 267                 return;
 268         if (continuing)
 269                 printf("\n");
 270         printf("==> %s <==\n", filename);
 271         continuing = 1;
 272         last_index = at_index;
 273 }
 274
 275 static void
 276 set_events(file_info_t *files)
 277 {
 278         int i, n;
 279         file_info_t *file;
 280         struct timespec ts;
 281
 282         ts.tv_sec = 0;
 283         ts.tv_nsec = 0;
 284
 285         n = 0;
 286         action = USE_KQUEUE;
 287         for (i = 0, file = files; i < no_files; i++, file++) {
 288                 if (file->fp == NULL)
 289                         continue;
 290                 if (Fflag && fileno(file->fp) != STDIN_FILENO) {
 291                         EV_SET(&ev[n], fileno(file->fp), EVFILT_VNODE,
 292                                EV_ADD | EV_ENABLE | EV_CLEAR,
 293                                NOTE_DELETE | NOTE_RENAME, 0, 0);
 294                         n++;
 295                 }
 296                 EV_SET(&ev[n], fileno(file->fp), EVFILT_READ,
 297                        EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0);
 298                 n++;
 299         }
 300
 301         if (kevent(kq, ev, n, NULL, 0, &ts) < 0)
 302                 action = USE_SLEEP;
 303 }
 304
 305 void
 306 follow(file_info_t *files, enum STYLE style, off_t off)
 307 {
 308         int active, i, n;
 309         long spin;
 310         file_info_t *file;
 311         struct stat sb2;
 312         struct timespec ts;
 313
 314         spin = 1;
 315
 316         /* Position each of the files */
 317         file = files;
 318         active = 0;
 319         n = 0;
 320         for (i = 0; i < no_files; i++, file++) {
 321                 if (file->fp) {
 322                         active = 1;
 323                         n++;
 324                         if (no_files > 1)
 325                                 showfilename(i, file->file_name);
 326                         forward(file->fp, style, off, &file->st);
 327                         if (Fflag && fileno(file->fp) != STDIN_FILENO)
 328                                 n++;
 329                 }
 330         }
 331
 332         if (!active)
 333                 return;
 334
 335         kq = kqueue();
 336         if (kq == -1)
 337                 err(1, "kqueue");
 338         ev = malloc(n * sizeof(struct kevent));
 339         if (ev == NULL)
 340                 err(1, "Couldn't allocate memory for kevents.");
 341         set_events(files);
 342
 343         for (;;) {
 344                 for (i = 0, file = files; i < no_files; i++, file++) {
 345                         if (file->fp == NULL)
 346                                 continue;
 347                         if (Fflag && fileno(file->fp) != STDIN_FILENO) {
 348                                 if (stat(file->file_name, &sb2) == -1) {
 349                                         /*
 350                                          * file was rotated, skip it until it
 351                                          * reappears.
 352                                          */
 353                                         continue;
 354                                 }
 355                                 if (sb2.st_ino != file->st.st_ino ||
 356                                     sb2.st_dev != file->st.st_dev ||
 357                                     sb2.st_nlink == 0) {
 358                                         file->fp = freopen(file->file_name, "r",
 359                                                            file->fp);
 360                                         if (file->fp == NULL) {
 361                                                 ierr();
 362                                                 continue;
 363                                         } else {
 364                                                 memcpy(&file->st, &sb2,
 365                                                        sizeof(struct stat));
 366                                                 set_events(files);
 367                                         }
 368                                 }
 369                         }
 370                         show(file, i);
 371                 }
 372
 373                 switch (action) {
 374                 case USE_KQUEUE:
 375                         ts.tv_sec = 1;
 376                         ts.tv_nsec = 0;
 377                         /*
 378                          * In the -F case, we set a timeout to ensure that
 379                          * we re-stat the file at least once every second.
 380                          */
 381                         n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
 382                         if (n == -1)
 383                                 err(1, "kevent");
 384                         if (n == 0) {
 385                                 /* timeout */
 386                                 break;
 387                         } else if (ev->filter == EVFILT_READ && ev->data < 0) {
 388                                 /* file shrank, reposition to end */
 389                                 if (lseek(ev->ident, 0, SEEK_END) == -1) {
 390                                         ierr();
 391                                         continue;
 392                                 }
 393                         }
 394                         break;
 395
 396                 case USE_SLEEP:
 397                         usleep(250000);
 398                         break;
 399                 }
 400         }
 401 }